Accurate determination of the shape and localization of metallic object(s) in X-ray CT imaging

Abstract

A binary image reconstruction method is provided to identify metal objects in a computer tomography (CT) image. The method includes providing a suitably programmed computer, providing a CT image, where the CT image includes intensity data, and the suitably programmed computer is used to determine a first range of attenuation coefficient values and a second range of attenuation coefficient values in the intensity data, where when a difference between the first range of attenuation coefficient values and the second range of attenuation coefficient values is less than a pre-determined gradient threshold value, a boundary of a metal object in the CT image is determined.

What is claimed: 
     
       1. A binary image reconstruction method to identify metal objects in a computer tomography (CT) image, comprising:
 a. providing a suitably programmed computer; 
 b. providing a CT image, wherein said CT image comprises intensity data, wherein said suitably programmed computer is used to determine a first range of attenuation coefficient values and a second range of attenuation coefficient values in said intensity data, wherein when a difference between said first range of attenuation coefficient values and said second range of attenuation coefficient values is less than a pre-determined gradient threshold value a boundary of a metal object in said CT image is determined. 
 
     
     
       2. The binary image reconstruction method of  claim 1 , wherein said determination of said attenuation coefficient ranges comprises applying a penalized weighted least squares (PLWS) criterion to minimize an objective function, wherein said objective function comprises a data fidelity term and a regularization term, wherein said regularization term characterizes an a priori attenuation coefficient of said intensity data. 
     
     
       3. The binary image reconstruction method of  claim 2 , wherein said regularization term is only applied for adjacent data elements having a gradient value smaller than a predetermined threshold value, wherein when said regularization term is applied to said CT image comprising metal object data or tissue data a reconstructed output image shows only a metal object and a masked patient structure background. 
     
     
       4. The binary image reconstruction method of  claim 1 , wherein said first range of attenuation coefficient values is assigned a value of 0 and said second range of attenuation coefficient values is assigned a value of 1, wherein a region in said CT image where said attenuation coefficient values change from 0 to 1 comprises a boundary of a metal object in said CT image.